UV layout doesn't match shape of the object
Seems like you have edited the object and didn't apply the scaling. If so, you have to apply the changes for your particular editing transformations such as Scaling and Rotating.


Go to the Object mode
Use &#9096; CtrlA and select an option.


This will apply your transformation changes to the object by setting the Scale to (1,1,1) and Rotation to (0,0,0).

See the documentation

Scaling object and UV Unwrap without applying transformation changes:



After applying changes: